DERIVATIVE FINANCIAL INTSTRUMENTS - Summary of Outstanding Swaptions (Details) - Payer Swaption [Member] - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Long [Member]
Derivatives, Fair Value [Line Items]
Swaption Cost	$ 29,390	$ 16,860
Net Estimated Fair Value	$ 26,282	$ 17,433
Derivative Instruments Average Months To Expiration	16 months 9 days	11 months
Notional Amount	$ 1,427,200	$ 500,000
Derivative Average Fixed Interest Rate	2.05%	1.26%
Term (Years)	12 years 2 months 12 days	9 years
Less Than Or Equal To One Year [Member] | Short [Member]
Derivatives, Fair Value [Line Items]
Swaption Cost	$ 13,400	$ 4,660
Net Estimated Fair Value	$ 10,358	$ 7,730
Derivative Instruments Average Months To Expiration	7 months 24 days	5 months 12 days
Notional Amount	$ 1,182,850	$ 507,700
Derivative Average Fixed Interest Rate	2.10%	1.49%
Term (Years)	11 years 7 months 6 days	12 years 9 months 18 days
Less Than Or Equal To One Year [Member] | Long [Member]
Derivatives, Fair Value [Line Items]
Swaption Cost	$ 4,000	$ 3,450
Net Estimated Fair Value	$ 1,959	$ 5
Derivative Instruments Average Months To Expiration	9 months 6 days	2 months 15 days
Notional Amount	$ 400,000	$ 675,000
Derivative Average Fixed Interest Rate	1.66%	0.95%
Term (Years)	5 years	4 years
One Year To Two Years [Member] | Long [Member]
Derivatives, Fair Value [Line Items]
Swaption Cost	$ 25,390	$ 13,410
Net Estimated Fair Value	$ 24,323	$ 17,428
Derivative Instruments Average Months To Expiration	19 months 3 days	17 months 12 days
Notional Amount	$ 1,027,200	$ 1,175,000
Derivative Average Fixed Interest Rate	2.20%	1.49%
Term (Years)	15 years	12 years 9 months 18 days